Preparation of photosetting coating composition



Patented Nov. 16, 1948 PREPARATION or rno'rosn'r'rme GOATING COMPOSITIONL 'flGera'ldL. Wendt,'New York, N. Y., assignor to Sun"hemicalCorporation, a corporation of Belaware No Drawing. Original applicationApril 27, 1044,

[Serial No. 533,060. Divided and this applica- 8 Claims.

fj'This, irivsnuon' relates to the preparation of coating andimpregnatingcompositions containing eleostearin, to the compositions soprepared, and tomethods for rapidly drying or setting thesecompositions,-

While there are many industries in which quickdrying coating onimpregnating compositions are desirableg'the printing industry is'one inwhich such com-positions are'oi great importance. Modern high'speed'press' operations require inks which will 'dry quickly"enough'to' avoid the difiiculties of smudgingfsnifearingando'fi's'etting. Printing at these highspeedshasbeen made possible by anumber-ofdevelopments, such as by modifying the-composition of the inksor the character of the surfaee to beprinted upon, =by'heating theprinted'webs orsheets, or by other means. The present inventiontherefore is particularly applicable in the printing industry, althoughit is not limited-thereto and may be used inother'fieldswhererapidly-drying; coating or impregnating compositions are desired-as in paints, varnishes, and the like. V

This application is a division of applicants -co-' pending implicationSerial No. 533,060, filed April 27', 1-944; which has become abandoned,which in turn is a.'-continuation of applicants earlier filedapplication LEierialNo. -266,682, filed April '7, 1939,

which has become abandoned.

3 Illustrat-ive'of the need for rapid drying or setting of theprintedimpression to non-offsetting condition before contact With a surfacewhich can cause offs'ettingor smearing or smudging are the speeds ofthe'traveling paper webs in present day high speed printing operations.These web speeds range for-example from 300 to 1800 feet per minute.Hence 5 procedures have been adopted for dryingiin avery shorttime-say 3ore seconds or less, and evensdown to fractions of a second. Because;if, anginkwere used which required say seconds to :dry or setupsuficiently so that it would not offset,- smear or smudge, the webwould a have to travel 50 120-300 feetbeforecontacting its printed facein offsettingv relation with any object, e.;g. before making a secondimpression or contactingwith'sa smearing or smudging part of the pressmechanism, or before winding, stacking, etc. i

1 Ordinarily the time required fora printing ink tosetupsdfficientlytoavoid offsetting is definitely lesdthan 'the time required for completedrying-or setting ot thesame ink. Again, the conditions whichpontributejtoward ofisetting vary more for less -thatis to say, the'amoiint of0dsetting'; smearing or smud'ging; or any given ink backing up, re-

tion August 21,1946, Serial No.'.692,151

at any given point in its drying obviously depends upon the amount ofpressure, slippingaction, or the likeapplied to the ink impression.

'It is therefore an object of the present-invention to'providecoatingand impregnating compositions which can under proper photosettingcon.- ditions be dried or set up rapidly to be-nomofisetting andnon-smudging.

Another object is to provide-such proper conditions for effecting rapiddrying or setting-of these compositions.

Another object is to provide inks,- and means for setting them withsufficient rapidity-which are particularly useful for high-speedprinting purposes.

Other objects will be evident from the present disclosure.

In the practicingof the present invention, compositions are preparedwhich comprise as-an'essential a substance made up largely or wholly 0feleostearin or keto eleostearin, and the said compositions also includesuch binders, pigments, solvent, orother materials as maybe required tomake them suitable for the usedesired. The present invention comprises,briefly, the preparation of a suitable composition of such kind which isessentially responsive to light of certain limited wave lengths of suchrange as to photoset with the required and desired rapidity to givenon-01T- setting or non-smudging or non-smearing'condition as stated;taking suitable steps to-accelerate appreciably the rapid set-up ordrying of'said composition under photosetting conditions subsequent toapplying it to the object to be coated, impregnated, or impressed;coating,impregnating or impressing the object with the composition; andthen subjecting the resulting object tolight of a suitable wave length;withor without otheraccelerating means, to photoset rapidly the coatingor impregnation.

It is found, in accordance with the present invention, that eleostearinand keto eleostearinare particularly susceptible to rapid photosettingunderthe influence of, or irradiation by, certain definite wave lengthbands of radiation which-are severally in the ultraviolet region. Thespeed of this photosetting can be'markedly accelerated by variousmeans,'-as by adding promoters or by'removing inhibitors, or both, aswill be discussed in greaterdetail below.

*Eleostearin is a natural product, which is the glyceryl ester ofeleostearic acid. It is found naturally', in the alphaform (L-e. astri-u eleostearin) in tung oil, and constitutes about to thereof. Asmall amount of the beta isomer is present in eleostearin and may bemade from the alpha isomer; and it is a solid. Both isomers are suitablefor use in the present invention, and both are included herein under theterm eleostearin..,

Keto eleostearin eleostearin in which all of the radicals of eleostearicacid are replaced by radicals of el-keto eleostearic acid (licanicacid). These radicals are also known as the eleostearate radicals andthe l-keto eleostearate or licanate radical respectively. Oiticica oilis largely keto eleostearin.

There are three conjugated double bonds in each of the acid radicals ofeleostearin and keto eleostearin. This configuration is potentiallyextremely reactive and I have found that when initiated and eifected bythe procedure of the present invention the drying of either eleostearinor keto eleostearin proceeds very rapidly to form a solidthree-dimensional molecular structure In this manner theeleostearin-containing compositions of this invention are rapidly set ordried. For convenience, therefore, theterm "eleostearin herein willinclude not only the isomers,,as above stated, but keto eleostearin aswell. The term eleostearin is also intended to include herein otherclosely related compounds of eleostearic acid or keto eleostearic acidwhich are characterized by containing at leasttwo radicals of one or theother of these acids. Thus, esters of these acids with polyhy- ,dricalcohols (of which glycerine is one) are included.

This'rapid setting or drying is effected, as already stated, by thecombined action of the accelerating means and of radiation of suitablewave lengths within the ultraviolet range.

While it is known that radiations within the ultraviolet and within theinfrared ranges, as well. as visible radiations, may have some physicalorchemic'al effectsupon various materials, including some oils used ininks; no one before has known, as I have discovered, that waves withineach of two, mutually exclusive, comparatively-narrow wave bands andeach of which is within the ultraviolet range, are particularlyspecific, but differently so, to effectuate rapid setting of inkmaterials containing the type of conjugated double bond system ineleostearin. One of these specific bands is the range of waves within2450-2600 A; and the other is within the 2800-3500 A. range, and thespecific and particular effectiveness of these two mutually exclusive,comparatively narrow wave bands, in the ultraviolet range, are bothdisclosed and claimed in my said copending application S. N. 533,060,and the companion application Serial No. 692,150, filed of even dateherewith as a division of said application S. N. 533,060 relates moreparticularly to my invention with respect to the particular band ofwaves Within the range 2800- 3500 A; while the instant application,which is alsoa division of my said application S. N. 533,060, relatesmore particularly to my invention with respect to the particular band ofwaves within the range 2450-2600 A.

The .range 2450-2600 A. appears to be specific to-ink materials havingthe type of conjugated double bond system in eleostearin when used tothe exclusion of objectionable waves outside said bandand-particularlyto the exclusion of waves within. the band 2800-3500 A., as set out insaid copending'application S. N. 533,060 and in my companion;application filed of even date herewithas a division thereof andhereinabove referred to; while the range 2800-3500 A. is likewisespecific in its own difl'erent way to ink materials having the type ofconjugated double bond system in eleostearin, when used to the exclusionofobjectionablewaves outside said particular band and withinthe'ultraviolet range, and particularly to the exclusion of waves withinthe other specific band or range of 2450-2600 A., to which this instantapplication relates. The products which result from the use of said2800- 3500 A. wave band have a smooth, glossy surface; while, incontrast if waves within the band 2450-2600 A. of the instant inventionare used the products which result have a dull or matte surface on thedried oil.

While I am not sure as to why the use of each of these two mutuallyexclusive and comparatively narrow wave bands, free from objectionablewaves within the ultraviolet range (which as stated is understood toinclude waves from about 200.0 A, below which substantially all of theradiations would be absorbed by the air, and up to approximately 4000'A., these limits depending for example upon the hazy or other radiationabsorbing conditions of the air, which latter marks approximately thedividing zone between the ultraviolet and the .visible radiations) Ihave found nevertheless that each of these two wave bands, when freefrom objectionable inhibiting quantities of waves within the ultravioletrange and outside the specific narrow band being used, and particularlywhen substantially free from waves within the other specified andmutually exclusive band, will have a very unusual and unexpectedspecific effect particularly upon materials having the characteristicssuch as the conjugated double bond system of eleostearin.

In accordance with the invention of the present divisional application,therefore, I have found, as stated above, that radiation within therange of 2450-2600 A, and with the waves within such 2450-2600 A. bandapplied for the setting operation while substantially free of themutually exclusive waves of the other specified band and free fromobjectionable quantities of other waves in the ultraviolet range, isparticularly eifective in causing rapid setting of such ink materials,containing selectively responsive constituent, such as eleostearin, toproduce rapidly set imprints which have a dried oil film with the dullor matte surface referred to.

Acceleration of the photosetting action of waves in this 2450-2600 A.band may be eifected by the use of promoters or by the removal ofinhibitors, or both. The degree or extent of acceleration will of coursedepend upon many factors, such as the type and quantity of promotersused, but I prefer to employ accelerating meanswhich will reduce by atleast 25%, and preferably by at least 50%, the time required forphotosetting under otherwise identical conditions.

Types of compounds suitable for promoters of the photosetting ofeleostearin under the conditions of the present invention are thosewhich are influenced by ultraviolet radiation to activate or releaseactive Br, I, and/or 0-.

One such type of promoter is blown eleostearin, which is convenientlyavailable in the form of blown tung oil or blown oi-ticica oil. Blowingof these oils results in the loss of some of the double bonds (i. e. insome loss of unsaturation) due to union with oxygen, probably includingthe formation of peroxides, together with some polymerization. Thisblowing may be carried out to a :apiser'r'zo .gneaten or liess'. extent,as desiredthat is, the 'ieleostearin may :be' only partly blown. As iswe'll lanowmz these 1011s .may 'bebodied by heat a'lon'e; howevergwdifierent productresults from that obrtained bytblowing. :This;resulting heat-bodied product has-undergone extensive polymerization,:Without the formationof: compounds with oxygen, andfds definitelyunsuited for use in the present torawr eleostearin acceleratesquicksetting as much-asdoes .theblowing of the eleostearin-or eyencmorei f-enough-of such promoters is used. Ihe mayalso beused to promote thesetting of bl loleo ar s I} :A-iewgof;these extraneous promoters are soreactive that they will cause the eleostearin compositions remaining;them to set up even on stariding,.- in .thedark. .Of those listed above,tetranitromethane issuch apromoter. Tetranitromethane .is more or lessunstable and hence care should be taken to avoid explosive conditions. 3Hence-such promoters as tetranitromethane would not be used when thecomposition is toibe'lseptffor any length of time before use.'Suchpromotersare, however, entirely suitable if adde th'compositionimmediately before use. IfIAlt'erna '13! to the procedure ofadding extraneous promoters to the compositions containingeleostearimfit'is possible to incorporate these promoters in the, paperor other surface or article to. be vGated 'orjimpregnated, whereuponthese promoters are "effective as soon asthe compositifon'fisf applied'to'such surface or article, and subje edjtdr diati'onpfappropriatelimited wave lengths as "described herein. In following this alternativeprocedure, however, "consideration should b'eYgiven' to the fact thatsome of the promotors are relatively volatile.

Another n'i'etho'dof accelerating the photoset ting of tungjandoiti'cica oils, which method may 'bef' use'd with'or without thepromoters, is to remove substances which inhibit the photosettingac'tion. 'Iung and oiticica oils characteristically cont'ainabout l'0'to15% of substances-other than 'oleostearin; More or less of thesesubstances can be removed -as by the method described below,

' and thoseihaving-a vapor pressure above (i. e. a

boiling 'point belowl that of eleostearin appear .t'ozhave inhibitingeffect on the photosetting. Imother words, for example, I have foundpurifiedeleostearin'more susceptible to the photosetting action byradiation of 2450-2600 A. wave length than a'rethe raw oils. Theseparation of thise i-nhib'i'tors :from the raw oils may be performed invarious ways. For example, it may beperformed1by :distillation, =.butmost ordinary methodsot distillation are-not suitable as theyresultweither in decomposition of the 'oil,: due to the high; heatrequired for distillation even at the ior'dinary icommercialrange oflowv pressures,

or -at least in heatbodying the oil, and hence in considerablepolymerization without formation'of oxygen-containing; promoting agents,which, as already stated, is to be avoided prior to subjecting-the.composition to the desired. wave length radiation. A suitable method ofdistillation is .that k nown as short-path molecular distillation,wherein the oil is flowed in a thin filmov'er a heated surface in a,chamber under extremely high vacuum, and as the molecules vaporize, theypass quickly toa-cooled surface situated-a relatively short-distancefrom .the heated surface. it is not necessary: nor even desirable todistill the-eleostearin itself; the =important point isto distill offthe inhibitors having a higher vapor pressure (lower boiling point).This type of distillation has been recently introduced commercially forthe separation of the constituents of more or less complex naturalmixtures which would be damaged or destroyed by attemptsto separate themby hitherto used distillation methods. 1

This procedure of removing inhibitors maybe used in conjunctionwithpromoterspromoters including both the blown eleostearin and-theextraneous promoters such as carbon-tetrabromide, etc. described above.I or .it may be used without promoters. In ordinary commercial practice,elimination of inhibitors would not ordinarily be performed, because ofthe expense of doing-so, although in some particular instances, as wherean extremely rapid photoset-ting is desired, such procedure may beadvantageously used in addition to the use of promoters. l

As already stated, one of the preferred wave lengths of the radiation toeffect rapidphotosetting is 2450-2600 A. The mercury spectrum line 2537A. falls in this region. However, most mercury I vapor ultraviolet lightsources now available commercially have, in addition, ultravioletradiation of the following characteristic wave length bands: 3126-3132A; 3650-3663 A.; 4047-4078 21.; 433913., and 4347-4358 IL, and each ofthese bands is present in an intensity'of about one to three times theintensity of the 2537 A. line. There are also generally minor amounts ofraldiation at other wave lengths, but these amounts are as a rule lessthan 10% of the amount of 2537 A. Y Some special light sources, however,such as the cold discharge mercury vapor tube, havethe bulk'of theradiation at the 2537 A. band; in the case of' this cold discharge tubethe total of the radiation intensities at other wave length bands,chiefly those mentioned above, is in the neighbo'rhood of 15% of thetotal radiation, while that at 2537 A .is about 85% of the total. Theconventional hot mercury arcs above referred to, however. have onlyabout10% of their radiation at'253'7 A, the other 99% comingchiefly at theother bands-as mentioned above. These hot arcs can be usedto efiectphotosetting in accordance withthe procedure of this invention, in atime comparable with that of the light sources which are-largely in the2537 A. band if these hot arcs are operated to produce an intensity atthe 2537 A; band of several times (say 5 to 10 times) that of the colddischarge tube or otherlight source of similar characteristics, i. e.,to approximate such radiation as is secured from the cold dischargemercury vapor tube, and if the detrimental radiation outside the2450-2600 A. range is sufficiently reduced asby-use of a suitablefilter,such as an aqueous solution.- of. a soluble nitrate,

e. g., sodium or potassium nitrate. I therefore prefer to use lightsources, such as the cold discharge mercury vapor tube, in which theradiation in the 2450-2600 A. range is sufiiciently larger than that inany other one band or range so that the efiective amount of such2450-2600 A. radiation is at least about 50% of the total radiation fromthe light source.

This cold discharge tube referred to above typically contains arelatively very small amount of mercury, and may also contain some argonas a starter. Larger amounts of mercury, as in the usual hot arcs,result in considerable reabsorption (and hence weakening relative toother bands) of the 2537 A. band.

The procedure of this invention may be conveniently carried out asfollows: A composition of the type desired is made up, using tung oroiticica oil or mixtures thereof, together with such other materials asmay be required-e. g., binders, solvents, other oils such as linseed,pigments, etc. Means for promoting the photosetting is effected, eitherby first blowing the tung or oiticica, oil, or by adding an extraneouspromoter of the type already described, or by removing inhibitors ofphotosetting -or by combinations of these. The composition is thenapplied to the object to be coated, impregnated or impressed-whichobject may be glazed or unglazed paper, or wood, cloth, glass, metal,synthetic resin sheets, regenerated cellulosic sheets, etc.--and thecoated or impressed surface is subjected to a source of light rich inradiation in the 2450-2600 A. range. The light source is placed as nearas conveniently possible to the coated surface, and is preferablyprovided with a reflector to concentrate the light upon the surface. Adistance of inch to 5 inches between the surface and the light sourcemay be used satisfactorily, for example.

-Heated air may sometimes be used to advantage to hasten the drying. Inplace of heated air, the paper or other surface to be coated orimpregnated may be heated; or both heated surface and heated air may beused. Driers, such as cobalt linoleate, mercury naphthenate, etc., maybe used in the composition, if desired, to assist in the setting anddrying.

As a modification of the present process, the eleostearin may be exposedin thin films to the action of radiation of the wave lengths preferredherein, prior to the application of the coating composition to theobject and prior to the final photosetting operation. Such preliminaryexposure is for the purpose of partially setting up the compositions, inorder to accelerate the final photosetting action. 1

The following will serve as a specific example of the operation of thepresent invention, with particular attention to its use in connectionwith printing in high-speed press operations.

A black printing ink of the following formula is prepared, the partsbeing by weight:

Parts Raw tung oil 40.0 Gum varnish 22.5 Stearin pitch 5.5 Wax compound3.0 Black pigment 17.0 Blue pigment 12.0

The gum varnish, stearin pitch, and wax compound are conventionalsubstances for making printing inks, and serve their usual functions.Thus, the stearin pitch assists in controlling length and flowcharacteristics, and the wax compound reduces tendency to offset. Thewax compound may be carnauba or other suitable wax dispersed in an oilsuch as linseed oil.

To parts of the foregoing ink composition add 10 parts of promoter, e.g. carbon tetrabromide.

The ink so prepared is used for printing in high speed press operationsin the usual manner. Then, as the paper leaves the printing means itsprinted surface is exposed to the radiation from a cold mercurydischarge tube, or a bank of such tubes, with suitable reflecting means,so that substantially all the radiation from said tube or tubes falls onthe printed surface. .The radiation from these tubes is such that, forexample, at least about 85% of it falls within the range of 2450-2600 A,and principally at 2537 A. By this procedure the ink is dried tonon-offsetting condition in a very short time, ranging from about twoseconds down to a small fraction of a second, when one tube is used. Theexact time depends upon thickness of the printed impression, surface orfinish of the paper, and severity of offset conditions, but underaverage working conditions the drying time to non-offsetting conditionwill be definitely less than one second. This time can also be shortenedstill further by having a plurality of tubes, so arranged that theprinted impression is subjected successively to the radiation from eachof these several tubes, for example. Thus each tube may extendtransversely the entire width of the web, and have its radiation portionsubstantially coextensive with said width, and a series of two or moreof these tubes, each with its own reflector and associated mechanism,may be placed at suitable intervals along the line of travel of the web.The distance between these intervals will obviously depend upon thespeed of the web, characteristics of ink and paper, and other factors,and should therefore be determined for each particular set ofconditions. The characteristics of some types of tubes may prevent theirextending the full width of the web, hence in such instances a series ofshorter tubes may be used, which series extends the full width of theweb. But with irradiation with the selected wave band drying tonon-offsetting or non-smudging condition may be attained within thespeed range stated by coordinating the controlling factors as stated.

The amounts of the various ingredients given in the foregoing examplemay be varied considerably or replaced by others, in accordance with thecharacteristics desired in the composition. The raw tung oil may bereplaced by oiticica oil; the amount used may be increased or decreasedabove or below the amount specified. However, it is preferable to-use atleast about 20% of raw or blown tung or oiticica oils or mixtures thereof, in ofder to give a composition which will photoset with sufiicientrapidity under the conditions of the procedure of the present invention.

The amount of extraneous promoter may vary considerably, depending uponthe nature of the promoter, the results desired, the time the ink mustbe kept before use, and thepresence or absence of inhibitors and ofinherent promoter (in the 'form of the blown oils). In the foregoingexample, for instance, the amount of carbon tetrabromide or itsequivalent may range between 1 and 20 parts per parts of the ink base,

depending on the speed of drying or setting desired.

It is to be understood that the foregoing disclosure is for the purposeof illustration of the present invention, and that various changes andmodifications may be made without departing from the spirit and scope ofthe invention as set forth in the appended claims.

What is claimed is:

1. Method of causing rapid setting of a coating composition whichcomprises applying a coatin composition containing as an essentialingredient not less than 20% of a compound having in its molecule atleast two radicals of the group consisting of eleostearate and ketoeleostearate and subjecting such applied composition to radiationcontrolled to contain essentially not less than approximately 50% withinthe wave length band 2450-2600 A.

2. Method of causing rapid setting of a coating composition whichcomprises applying a coating composition containing as essentialingredients not less than 20% of a compound havin in its molecule atleast two radicals of the group consisting of the eleostearate radicaland the keto eleostearate radical, and subjecting such appliedcomposition to radiation controlled to contain essentially not less thanapproximately 50% Within the wave length band 2450-2600 A, and toexclude any substantial proportion of any wave length of the band2800-3500 A.

3. Method of causing rapid setting of a coating composition whichcomprises applying a coating composition containing a photosettingpromoter and, as an essential ingredient, not less than 20 per cent of acompound having in its molecule at least two radicals of the groupconsisting of eleostearate and keto eleostearate and subjecting suchapplied composition to radiation controlled to contain essentially notless than approximately 50 per cent within the wave length band2450-2600 A.

4. Method of causing rapid setting of a coating composition whichcomprises applying a coating composition containing as an essentialingredient not less than 20 per cent of a compound having in itsmolecule at least two radicals of the group consisting of eleostearateand keto eleostearate and from which compound a substantial amount ofsubstances having vapor pressure above that of eleostearin have beenremoved and subjecting such applied composition to radiation controlledto contain essentially not less than approximately 50 per cent withinthe Wave length band 2450-2600 A.

5. Method of causing rapid setting of a coating composition whichcomprises applying a coating composition containing a photosettingpromoter and, as an essential ingredient, not less than 20 per cent of acompound having in its molecule at least two radicals of the groupconsisting of eleostearate and keto eleostearate and from which compounda substantial amount of substances having vapor pressure above that ofeleostearin have been removed and subjecting such applied composition toradiation controlled 10 to contain essentially not less thanapproximately per cent within the Wave length band 2450- 2600 A.

6. Method of causing rapid setting of a coating composition whichcomprises applying a coating composition containing a photosettingpromoter and, as essential ingredients, not less than 20 per cent of acompound having in its molecule at least two radicals of the groupconsisting of the eleostearate radical and the keto eleostearateradical, and subjecting such applied composition to radiation controlledto contain essentially not less than approximately 50 per cent withinthe wave length band 2450-2600 A, and to exclude any substantialproportion of any wave length of the band 2800-3500 A.

7. Method of causing rapid setting of a coating composition whichcomprises applying a coating composition containing as essentialingredient-s not less than 20 per cent of a compound having in itsmolecule at least two radicals of the group consisting of theeleostearate radical and the keto eleostearate radical, and from whichcompound a substantial amount of substances having vapor pressure abovethat of eleostearin have been removed and subjecting such appliedcomposition to radiation controlled to contain essentially not less thanapproximately 50 per cent within the wave length band 2450-2600 A, andto exclude any substantial proportion of any wave length of the band2800-3500 A.

8. Method of causing rapid setting of a coating composition whichcomprises applying a coating composition containing a photosettingpromoter and, as essential ingredients not less than 20 per cent of acompound having in its molecule at least two radicals of. the groupconsisting of the eleostearate radical and the keto eleostearateradical, and from which compound a substantial amount of substanceshaving vapor pressure above that of eleostearin have been removed andsubjecting such applied composition to radiation controlled to containessentially not less than approximately 50 per cent within the wavelength band 2450-2600 A, and to exclude any substantial proportion ofany wave length of the band 2800-3500 A.

GERALD L. WENDT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS OTHER REFERENCES Chemical and MetallurgicalEngineering, September 17, 1923, page 533.

American Pressman, September 1931, pages 27-30.

